The field of this invention generally includes hoists and cranes and in particular it includes devices for addition to existing hoists and cranes to prevent the suspended ends of their lifting lines from swaying laterally. In many applications where cranes and hoists are used, it is important that the suspended ends of the lifting lines do not sway laterally. Such lateral swaying can result from movements of the crane or hoist or from forces acting directly on the lifting lines or on the object being lifted. The most common prior art approach to preventing such lateral swaying has been to use several lifting lines attached to the same object with the lifting lines suspended at different angles to form an inverted pyramid pattern. This approach requires that the hoist or crane have several extra takeup reels, pulleys and structures to support the required synchronized or controlled high torque reels. These reels have to be powered or equipped with damping brakes. It would be very difficult if not impossible to modify most existing hoists or cranes to be anti-sway by adding such additional lifting lines to make such an inverted pyramid. It is one of the objectives of this invention to provide a device for existing hoists or cranes with which these hoists or cranes may be modified to limit the lateral swaying of the suspended ends of their lifting lines.
It is another objective of this invention to provide such an anti-sway device that is relatively simple and easy to operate.
It is another objective of this invention to provide such an anti-sway capability in a second vertical tangential plane for boom cranes which already have a conventional tagline type anti-sway system in a radial vertical plane through the crane's vertical revolvement axis.
It is another objective of this invention to provide an anti-sway device which can perform the alternative function of serving as an independent failsafe load holding device.